1. Field of the Invention
The present invention relates to a dipole antenna, and more particularly, to a compact dipole antenna for a radio frequency identification (RFID) tag capable of being used in an RFID-ultra high frequency (UHF) band, easily performing a conjugate impedance matching between an antenna and an RFID tag chip and miniaturization, and increasing a reading distance and a received power by generating circular polarization.
2. Discussion of Related Art
Generally, radio frequency identification (RFID), which is a technique in which information included in a tag is detected and recorded using a radio frequency in a non-contact method, is a technique capable of detecting, tracing, and managing a tagged object, animal, person, and the like.
An RFID system includes a tag (or a transponder) having unique identification information that is attached to an object, an animal, or the like, and a reader (or an interrogator) for reading or recording the identification information included in the tag.
Generally, the RFID tag is configured of an integrated circuit (IC) chip, and an antenna, an RF transceiving circuit, a control logic, and a memory are embedded in the IC chip, and a radio frequency is transceived through the antenna.
The RFID tag reflects a signal in a specific RF band transmitted from the reader, changes information including the identification information in the reflected RF signal, and transmits the RF signal to the reader.
The antenna used in the RFID tag has a dipole antenna pattern printed on a film. That is, a characteristic of the antenna applied to the RFID tag is designed in a pattern shape of the dipole antenna.
However, the antenna used in the RFID tag generates linear polarization (LP), and thus only half of a transmission power is received by the tag due to a polarization mismatch phenomenon between the reader, which generally generates circular polarization, and the tag. As a result, there is a problem that a maximum reading range of the antenna is reduced.
Related art of Korea Unexamined Patent Application Publication No. 10-2011-0020617 (Title: CIRCULARLY POLARIZED ANTENNA FOR UHF BAND RFID READER, Published on Mar. 3, 2011) exists.